Apparatus and method for reducing optical cross-talk in image sensors

ABSTRACT

An image sensor device includes a semiconductor substrate having a front surface and a back surface; an array of pixels formed on the front surface of the semiconductor substrate, each pixel being adapted for sensing light radiation; an array of color filters formed over the plurality of pixels, each color filter being adapted for allowing a wavelength of light radiation to reach at least one of the plurality of pixels; and an array of micro-lens formed over the array of color filters, each micro-lens being adapted for directing light radiation to at least one of the color filters in the array. The array of color filters includes structure adapted for blocking light radiation that is traveling towards a region between adjacent micro-lens.

BACKGROUND

The present disclosure relates generally to image sensor devices and,more particularly, to an apparatus and method for reducing opticalcrosstalk in image sensor devices.

An image sensor provides a grid of pixels which may containphotosensitive diodes or photodiodes, reset transistors, source followertransistors, pinned layer photodiodes, and/or transfer transistors forrecording intensity or brightness of light. The pixel responds to thelight by accumulating photo-charges—the more light, the more thephoto-charges. The charges can then be used by another circuit so that acolor and brightness can be used for a suitable application, such as adigital camera. Common types of pixel grids include a charge-coupleddevice (CCD), a complimentary metal oxide semiconductor (CMOS) imagesensor (CIS), an active-pixel sensor (APS), and a passive-pixel sensor.

In order to capture color information, image sensors may employ a colorfilter layer that incorporates several different color filters (e.g.,red, green, and blue), and are positioned such that the incident lightis directed through the filter via an array of micro-lens. However, themicro-lens may exhibit poor light control ability at a region betweenadjacent micro-lens. That is, incident light traveling through thisregion may not be directed to the appropriate pixel for processing. Thismay result in optical cross-talk between adjacent pixels and thus, maylead to poor device performance.

Therefore, what is needed is a simple and cost-effective apparatus andmethod for reducing optical cross-talk in image sensor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isemphasized that, in accordance with the standard practice in theindustry, various features are not drawn to scale. In fact, thedimensions of the various features may be arbitrarily increased orreduced for clarity of discussion.

FIG. 1 is a top view of an image sensor including a plurality of pixels.

FIGS. 2A & 2B are cross-sectional and top views, respectively, of partof the image sensor of FIG. 1.

FIG. 3 is a flowchart of a method of making a back-side illuminatedsensor that embodies various aspects of the present disclosure.

FIGS. 4A-4C are cross-sectional views of the back-side illuminated imagesensor being processed according to the method of FIG. 4.

FIG. 5 is a flowchart of a method of making a back-side illuminatedsensor according to an alternative embodiment of the present disclosure.

FIGS. 6A-6C are cross-sectional views of the back-side illuminated imagesensor being processed according to the method of FIG. 5.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments, or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. These are merelyexamples and are not intended to be limiting. In addition, the presentdisclosure may repeat reference numerals and/or letters in the variousexamples. This repetition is for the purpose of simplicity and clarityand does not in itself dictate a relationship between the variousembodiments and/or configurations discussed. Moreover, the formation ofa first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed interposing the first and secondfeatures, such that the first and second features may not be in directcontact.

Referring to FIG. 1, illustrated is a top view of an image sensor 10including a plurality of pixels 20. Additional circuitry andinput/outputs 30 are typically provided adjacent to the grid of pixels20 for providing an operation environment for the pixels and forsupporting external communications with the pixels. The image sensor 10may include a charge-coupled device (CCD), complimentary metal oxidesemiconductor (CMOS) image sensor (CIS), an active-pixel sensor (APS),and a passive-pixel sensor.

Referring to FIGS. 2A and 2B, illustrated are cross-sectional and topviews, respectively, of two adjacent pixels 20 of the image sensor 10FIG. 1. In the present example, the adjacent pixels include a firstpixel 102 and a second pixel 104 for sensing visible light. It isunderstood that the use of visible light is a mere example and thatother types of radiation such as infrared (IR), microwave, X-ray, andultraviolet (UV) may be used in other types of applications. The pixels102 and 104 may be formed on a semiconductor substrate 110. Thesubstrate 110 may include a front surface 111 and a back surface 112.The substrate 110 may comprise an elementary semiconductor such assilicon, germanium, and diamond. Alternatively, the substrate 110 mayoptionally comprise a compound semiconductor such as silicon carbide,gallium arsenic, indium arsenide, and indium phosphide. Additionally,semiconductor substrate types such as silicon-on-insulator (SOI) and/oran epitaxial layer may be utilized.

The pixels 102 and 104 may each comprise of a photodiode and at leastone transistor 114 and 116 for sensing and recording an intensity oflight. An example of a photodiode that can be used in this embodiment isshown in U.S. patent application Ser. No. 11/291,880, filed on Dec. 1,2005, which is hereby incorporated by reference. For example, thesubstrate 110 may comprises a P-type silicon. A silicon epitaxial layer(epilayer or epi) may be grown on the substrate 110 by a method such aschemical vapor deposition (CVD). The epilayer may have a lowerconcentration of dopant than that of the heavily doped P-type siliconsubstrate 110. The photodiode includes a light-sensing region which inthe present embodiment is an N-type doped region 122 and 124 havingdopants formed in the silicon epilayer. All doping may be implementedusing a process such as ion implantation or diffusion in various stepsand techniques. It is understood that all doping may be reversedaccordingly such as providing an N-type silicon substrate having anepilayer with a P-type light-sensing region.

The substrate 110 may also comprise lateral isolation features (notshown) such as shallow trench isolation (STI) features to separate thepixels and/or other devices formed on the substrate. These other devicesmay include various doped regions each having an N-type or P-type, suchas an N-well or P-well. Even though the present example describes aphotodiode, it is understood that other types of pixels may be used.Other types of pixels include, but are not limited to, pinnedphotodiodes, photo transistors (e.g., p/n/p or n/p/n), and photogates.Additionally, configurations such as a 4T active pixel including aphotodiode and four transistors (e.g., transfer gate transistor, resettransistor, source follower transistor, and select transistor) or pixeltypes using 4T operating concepts (e.g., sharing reset transistor andsource follower transistor for several pixels) may be used for thepixels. Additional circuitry also exists to provide an appropriatefunctionality to handle the type of pixels 100 being used and the typeof light being sensed.

The image sensor 10 includes a plurality of interconnect metal layersincluding first and second interconnect metal layers 130 and 132,respectively, overlying the pixels 102 and 104. The metal layers 130 and132 may be used for interconnecting various devices formed on thesubstrate 110. The metal layers 130 and 132 may comprise of conductivematerials such as aluminum, aluminum alloy, copper, copper alloy,titanium, titanium nitride, tungsten, polysilion, metal silicide, and/orcombinations thereof. The image sensor 10 may further include aninter-metal dielectric 134 for insulating the interconnecting metallayers 130 and 132 disposed therein. The inter-metal dielectric 134 maycomprise of a low-k dielectric material such as a material having adielectric constant (k) less than about 3.5. The inter-metal dielectric134 may comprise of carbon-doped silicon oxide, fluorine-doped siliconoxide, silicon nitride, silicon oxynitride, polymide, spin-on glass,amorphous fluorinated carbon, and/or other suitable materials. Eventhough two metal layers 130 and 132 and inter-metal dielectric 134 isdisclosed herein for clarity and simplicity, it is understood thatmultiple metal layers and inter-metal dielectric are typically used inan image sensor device.

The image sensor 10 further includes a color filter layer overlying theback surface 112 of the substrate 110. In the present example, the colorfilter layer includes a first color filter 142 for filtering throughvisible light of a first wavelength (e.g., red, blue, green light) tothe first pixel 102, and a second color filter 144 for filtering throughvisible light of a second wavelength (e.g., red, blue, green light) tothe second pixel 104. The color filters 142 and 144 may comprise of adye-based (or pigment-based) polymer for filtering out a specificfrequency band (e.g., desired wavelength of light). Alternatively, thecolor filters 142 and 144 may optionally comprise of a resin or otherorganic-based material having color pigments.

The image sensor 10 further includes a plurality of micro-lens 150. Themicro-lens 150 may be positioned in various arrangements overlying thecolor filters 142 and 144 and pixels 102 and 104. The micro-lens 150 mayhave a variety of shapes depending on the refractive index of materialused for the micro-lens and the distance from the sensor surface to themicro-lens.

In operation, the image sensor 10 is designed to receive light radiationtraveling towards the back surface 112 of the semiconductor substrate110. The visible light is directed towards the color filters 142 and 144by the micro-lens 150. The light passing through to the color filters142 and 144 and pixels 102 and 104 may be maximized since the light isnot obstructed by various device features (e.g., gates electrodes) ormetal features (e.g., the metal layers 130 and 132) overlying the frontsurface 111 of the substrate 110. The desired wavelength of light (e.g.,red, green, blue light) that is allowed to pass through to therespective pixel 102 and 104, induces a photocurrent which may berecorded and processed. However, there is a region 160 between adjacentmicro-lens 150 where the micro-lens exhibit poor light control ability.That is, light traveling through this region 160 may not be directed tothe appropriate pixel for processing. As such, optical cross-talkbetween adjacent pixels may occur and thus, may lead to poor deviceperformance.

Referring to FIGS. 3, and 4A through 4C, illustrated are a flowchart ofa method 300 for making a back-side illuminated image sensor device 400,and cross-sectional views of the image sensor 400 being processed atvarious stages according to the method 300. The image sensor 400 of FIG.4 is similar to the image sensor 10 of FIGS. 1-2 except for the featuresdisclosed below. Similar features in FIGS. 4 and 1-2 are numbered thesame for clarity. In FIG. 3, the method 300 begins with step 302 inwhich a semiconductor substrate 110 may be provided with a front surface111 and a back surface 112. The substrate 110 may include an epilayerformed thereon. The method 300 continues with step 304 in which aplurality of pixels 102 and 104 may be formed on the substrate 110, eachpixel having a light-sensing element 122 and 124 such as a photodiode,and at least one transistor 114 and 116. The process of forming thepixels is known in the art and thus, not described in detail here.

The method 300 continues with step 306 in which interconnect metallayers 130 and 132 and an inter-metal dielectric 134 may be formed overthe substrate 110. The process of forming the interconnect metal layersand inter-metal dielectric is known in the art and thus, not describedin detail here. The method 300 continues with step 308 in which aplanarization layer 402 may be formed over the back surface 112 of thesubstrate 110. The planarization layer 402 may include silicon oxide.Alternatively, the planarization layer 402 may optionally includesilicon nitride, silicon oxynitride, or other suitable material. Theplanaratization layer 402 may be formed by a suitable deposition orspin-coating process known in the art. The method 300 continues withstep 310 in which the planarization layer 402 may be patterned byphotolithography and etched to define open regions 404 and 406 withinthe planarization layer. The open regions 404 and 406 may have a widthof about 0.2 μm. Alternatively, the open regions 404 and 406 mayoptionally have a width smaller than 0.2 μm.

In FIG. 4A, the method 300 continues with step 312 in which a blackphotoresist layer 410 may be formed over the patterned planarizationlayer 402. Accordingly, the black photoresist layer 410 may fill in theregions 404 and 406 within the planarization layer 402. The blackphotoresist layer 410 may be formed by a deposition process,spin-coating process, or other suitable process. Alternatively, othersuitable opaque materials may optionally be used instead of the blackphotoresist. In FIG. 4B, the method 300 continues with step 314 in whichthe black photoresist layer 410 may be etched back until theplanarization layer 402 is exposed. The etch back process includes anetching species that selectively removes the black photoresist layer 410and uses the planarization layer 402 as an etch stop layer.

In FIG. 4C, the method 300 continues with step 316 in which a colorfilter layer including color filters 142 and 144 may be formed over thepatterned planarization layer 402. The color filter layer may beconfigured such that a region between adjacent color filters 142 and 144substantially overlies the regions 404 and 406 within the planarizationlayer 402 that are filled with the black photoresist. The method 300continues with step 318 in which a pluraltiy of micro-lens 150 may beformed over the color filter layer. The micro-lens 150 are configured todirect light radiation traveling towards the back surface 112 of thesubstrate 110 to the corresponding pixels 102 and 104. The micro-lens150 may be configured such that a region between adjacent micro-lens 150substantially overlies the regions 404 and 406 within the planarizationlayer 402 that are filled with the black photoresist.

In operation, the image sensor 400 is designed to receive lightradiation traveling towards the back surface 112 of the semiconductorsubstrate 110. The light is directed towards the color filters 142 and144 by the micro-lens 150. The light passing through to the colorfilters 142 and 144 and pixels 102 and 104 may be maximized since thelight is not obstructed by various device features (e.g., gateselectrodes) or metal features (e.g., the metal layers 130 and 132)overlying the front surface 111 of the substrate 110. The desiredwavelength of light (e.g., red, green, blue light) that is allowed topass through to the respective pixel 102 and 104, induces a photocurrentwhich may be recorded and processed. There is a region 420 betweenadjacent micro-lens 150 where the micro-lens exhibit poor light controlability. That is, light traveling through this region 420 may not bedirected to the appropriate pixel for processing. However, in thepresent embodiment, the light traveling through this region 420 may beshielded or blocked by the regions 404 and 406 within the planarizationlayer 402 that are filled with the black photoresist. As such, theregions 404 and 406 within planarization layer 402 may minimize opticalcross-talk between adjacent pixels.

Referring to FIGS. 5, and 6A through 6C, illustrated are a flowchart ofa method 500 for making a back-side illuminated image sensor device 600,and cross-sectional views of the image sensor 600 being processed atvarious stages according to the method 500. The image sensor 600 of FIG.6 is similar to the image sensor 10 of FIGS. 1-2 except for the featuresdisclosed below. Similar features in FIGS. 6 and 1-2 are numbered thesame for clarity. In FIG. 5, the method 500 begins with step 502 inwhich a substrate 110 may be provided with a front surface 111 and aback surface 112. The substrate 110 may include an epilayer formedthereon. The method 500 continues with step 504 in which a plurality ofpixels 102 and 104 may be formed on the substrate 110, each pixel havinga light-sensing element 122 and 124 such as a photodiode, and at leastone transistor 114 and 116. The process of forming the pixels is knownin the art and thus, not described in detail here.

The method 500 continues with step 506 in which interconnect metallayers 130 and 132 and an inter-metal dielectric 134 may be formed overthe substrate 110. The process of forming the interconnect metal layersand inter-metal dielectric is known in the art and thus, not describedin detail here. The method 500 continues with step 508 in which aplanarization layer 602 may be formed over the back surface 112 of thesubstrate 110. The planarization layer 602 may include silicon oxide.Alternatively, the planarization layer 602 may optionally includesilicon nitride, silicon oxynitride, or other suitable material. Theplanaratization layer 602 may be formed by a suitable deposition orspin-coating process known in the art.

The method 500 continues with step 510 in which a color filter layer maybe formed over the planarization layer 602. The color filter layerincludes a first color filter 142 for filtering through visible light ofa first wavelength (e.g., red, blue, green light) to the first pixel102, and a second color filter 144 for filtering through visible lightof a second wavelength (e.g., red, blue, green light) to the secondpixel 104. The color filters 142 and 144 may comprise of a dye-based (orpigment-based) polymer for filtering out a specific frequency band(e.g., desired wavelength of light). Alternatively, the color filters142 and 144 may optionally comprise of a resin or other organic-basedmaterial having color pigments. The process of forming the color filterlayer is known in the art, and thus, not described in detail here.

The method 500 continues with step 512 in which the color filter layermay be patterned by photolithography and etched to define open regions604 and 606 within the color filter layer. The open regions 604 and 606are located between adjacent color filters 142 and 144. The open regions604 and 606 may have a width of about 0.2 μm. Alternatively, the openregions 604 and 606 may optionally have a width smaller than 0.2 μm. InFIG. 6A, the method 500 continues with step 514 in which in which ablack photoresist layer 610 may be formed over the patterned colorfilter layer. Accordingly, the black photoresist layer 610 may fill inthe regions 604 and 606 between adjacent color filters 142 and 144. Theblack photoresist layer 610 may be formed by a deposition process,spin-coating process, or other suitable process. Alternatively, othersuitable opaque materials may optionally be used instead of the blackphotoresist.

In FIG. 6B, the method 500 continues with step 516 in which the blackphotoresist layer 610 may be etched back until the color filters 142 and144 are exposed. The etch back process includes an etching species thatselectively removes the black photoresist layer 110 and uses the colorfilter layer as an etch stop layer. In FIG. 6C, the method 500 continueswith step 518 in which a plurality of micro-lens 150 may be formed overthe color filter layer. The micro-lens 150 are configured to directlight radiation traveling towards the back surface 112 of the substrate110 to the corresponding pixels 102 and 104. The micro-lens 150 may beconfigured such that a region between adjacent micro-lens 150substantially overlies the regions 604 and 606 within the color filterlayer that are filled with the black photoresist.

In operation, the image sensor 600 is designed to receive lightradiation traveling towards the back surface 112 of the semiconductorsubstrate 110. The light is directed towards the color filters 142 and144 by the micro-lens 150. The light passing through to the colorfilters 142 and 144 and pixels 102 and 104 may be maximized since thelight is not obstructed by various device features (e.g., gateselectrodes) or metal features (e.g., the metal layers 130 and 132)overlying the front surface 111 of the substrate 110. The desiredwavelength of light (e.g., red, green, blue light) that is allowed topass through to the respective pixel 102 and 104, induces a photocurrentwhich may be recorded and processed. There is a region 620 betweenadjacent micro-lens 150 where the micro-lens exhibit poor light controlability. That is, light traveling through this region 620 may not bedirected to the appropriate pixel for processing. However, in thepresent embodiment, the light traveling through this region 620 may beshielded or blocked by the regions 604 and 606 within the color filterlayer that are filled with the black photoresist. As such, the regions604 and 606 between adjacent color filters 142 and 144 may minimizeoptical cross-talk between adjacent pixels 102 and 104.

Thus, provided is an image sensor and method for making the same. In oneembodiment, an image sensor device includes a semiconductor substratehaving a front surface and a back surface; a plurality of pixels formedon the front surface of the semiconductor substrate, each pixel beingadapted for sensing light radiation; an array of color filters formedover the plurality of pixels, each color filter being adapted forallowing a wavelength of light radiation to reach at least one of theplurality of pixels; and a plurality of micro-lens formed over the arrayof color filters, each micro-lens being adapted for directing lightradiation to at least one of the color filters in the array. The arrayof color filters further includes structure adapted for blocking lightradiation that is traveling towards a region between adjacentmicro-lens. In some embodiments, the array of color filters is formedover the back surface of the substrate. In some other embodiments, thestructure includes a black photoresist disposed in a space betweenadjacent color filters in the array.

In other embodiments, the image sensor device further includes aplanarization layer formed between the back surface of the substrate andthe array of color filters. In still other embodiments, the structureincludes a planatization layer having a transparent portion and anopaque portion, the planarization layer being disposed between the backsurface of the substrate and a bottom surface of the array of colorfilters, the opaque portion being disposed underneath an area betweenadjacent color filters. In some other embodiments, the opaque portionincludes a black photoresist. In other embodiments, the transparentportion is one of a silicon oxide, a silicon nitride, a siliconoxynitride, or combinations thereof. In other embodiments, the structurehas a width that is equal to about 0.2 μm. In still other embodiments,the device further includes a plurality of interconnect metal layersformed over the front surface of the substrate; and an inter-metaldielectric disposed between each of the plurality of metal layers.

Also provided is one embodiment of a method for making an image sensordevice. The method includes the steps of: providing a semiconductorsubstrate having a front surface and a back surface; forming a pluralityof pixels on the front surface of the semiconductor substrate, eachpixel being adapted for sensing light radiation; forming an array ofcolor filters over the plurality of pixels, each color filter beingadapted for allowing a wavelength of light radiation to reach at leastone of the plurality of pixels; and forming a plurality of micro-lensover the array of color filters, each micro-lens being adapted fordirecting light radiation to at least one of the color filters in thearray. The step of forming the array of color filters further includesforming the array of color filters with structure adapted for blockinglight radiation traveling towards a region between adjacent micro-lens.

In some embodiments, the step of forming the array of color filters withthe structure includes: forming a planarization layer on the backsurface of the substrate; patterning the planarization layer to define aspace within the planarization layer; forming a layer of an opaquematerial over the patterned planarization layer; etching back the opaquematerial until the planarization layer is exposed; and forming a colorfilter layer over the planarization layer such that the space filledwith the opaque material is disposed underneath an area between adjacentcolor filters. In some embodiments, the step of forming the layer ofopaque material includes forming a layer of a black photoresist.

In some other embodiments, the step of forming the array of colorfilters with the structure includes: forming a planarization layer onthe back surface of the substrate; forming a color filter layer over theplanarization layer; patterning the color filter layer to define a spacebetween adjacent color filters; forming a layer of an opaque materialover the patterned color filter layer; and etching back the opaquematerial until the color filter layer is exposed. In some embodiments,the step of forming the layer of opaque material includes forming alayer of a black photoresist. In still other embodiments, the methodfurther includes: forming a plurality of metal layers over the frontsurface of the substrate; and forming an intermetal dielectric betweeneach of the plurality of metal layers.

Also provided is a semiconductor device including a substrate having afront surface and a back surface; a plurality of pixels formed on thefront surface of the substrate, each pixel being adapted to sense lightradiation directed towards the back surface of the substrate; an arrayof color filters formed over the back surface of the substrate, eachcolor filter being aligned with one of the plurality of pixels forallowing a wavelength of light radiation to pass through to the one ofthe plurality of pixels; a plurality of micro-lens formed over the arrayof color filters, each micro-lens being adapted to direct lightradiation to each color filter in the array; and a blocking structuredisposed between the back surface of the substrate and the plurality ofmicro-lens, the blocking structure being adapted to block lightradiation traveling towards a region between adjacent micro-lens fromreaching the pixels.

In some embodiments, the blocking structure includes a black photoresistdisposed in a region between adjacent color filters. In some otherembodiments, the blocking structure includes a planarization layerformed between the back surface of the substrate and a bottom surface ofthe array of color filters, the planarization layer having a blackphotoresist disposed underneath an area between adjacent color filters.In still other embodiments, the wavelength of light is one of a redlight, a green light, and a blue light. In other embodiments, each pixelincludes a photodiode and at least one transistor.

The foregoing has outlined features of several embodiments so that thoseskilled in the art may better understand the detailed description thatfollows. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein. Forexample, the color filters disclosed may be configured to filter throughother colors such as cyan, yellow, and magenta, or other types of lightradiation such as infrared (IR), microwave, X-ray, and ultraviolet (UV).Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure.

Several different advantages exist from these and other embodiments. Inaddition to providing an efficient and cost-effective apparatus andmethod for reducing optical cross-talk in image sensors, the apparatusand method disclosed herein can easily be integrated with currentsemiconductor processing equipment and techniques. In addition, theapparatus and method disclosed herein utilizes a black photoresistmaterial that does not exhibit good resolution in photolithography forsmall feature sizes. As such, the apparatus and method disclosed hereinmay be implemented even as pixel sizes continue to decrease withemerging technologies.

1. An image sensor device, comprising: a semiconductor substrate havinga front surface and a back surface; a plurality of pixels formed on thefront surface of the semiconductor substrate, each pixel being adaptedfor sensing light radiation; an array of color filters formed over theplurality of pixels, each color filter being adapted for allowing awavelength of light radiation to reach at least one of the plurality ofpixels; and a plurality of micro-lens formed over the array of colorfilters, each micro-lens being adapted for directing light radiation toat least one of the color filters in the array; wherein the array ofcolor filters further includes a structure adapted for blocking lightradiation that is traveling towards a region between adjacentmicro-lens.
 2. The device of claim 1, wherein the array of color filtersis formed over the back surface of the substrate.
 3. The device of claim2, wherein the structure includes a black photoresist disposed in aspace between adjacent color filters in the array.
 4. The device ofclaim 3, further comprising a planarization layer formed between theback surface of the substrate and the array of color filters.
 5. Thedevice of claim 1, wherein the structure includes a planatization layerhaving a transparent portion and an opaque portion, the planarizationlayer being disposed between the back surface of the substrate and abottom surface of the array of color filters, the opaque portion beingdisposed underneath an area between adjacent color filters.
 6. Thedevice of claim 5, wherein the opaque portion includes a blackphotoresist.
 7. The device of claim 5, wherein the transparent portionis one of a silicon oxide, a silicon nitride, a silicon oxynitride, orcombinations thereof.
 8. The device of claim 1, wherein the structurehas a width that is equal to about 0.2 μm.
 9. The device of claim 1,further comprising: a plurality of interconnect metal layers formed overthe front surface of the substrate; and an inter-metal dielectricdisposed between each of the plurality of metal layers.
 10. A method formaking an image sensor device, comprising: providing a semiconductorsubstrate having a front surface and a back surface; forming a pluralityof pixels on the front surface of the semiconductor substrate, eachpixel being adapted for sensing light radiation; forming an array ofcolor filters over the plurality of pixels, each color filter beingadapted for allowing a wavelength of light radiation to reach at leastone of the plurality of pixels; and forming a plurality of micro-lensover the array of color filters, each micro-lens being adapted fordirecting light radiation to at least one of the color filters in thearray; wherein the forming the array of color filters further includesforming the array of color filters with a structure adapted for blockinglight radiation traveling towards a region between adjacent micro-lens.11. The method of claim 10, wherein the forming the array of colorfilters with the structure includes: forming a planarization layer onthe back surface of the substrate; patterning the planarization layer todefine a space within the planarization layer; forming a layer of anopaque material over the patterned planarization layer; etching back theopaque material until the planarization layer is exposed; and forming acolor filter layer over the planarization layer such that the spacefilled with the opaque material is disposed underneath an area betweenadjacent color filters.
 12. The method of claim 11, wherein the formingthe layer of opaque material includes forming a layer of a blackphotoresist.
 13. The method of claim 10, wherein the forming the arrayof color filters with the structure includes: forming a planarizationlayer on the back surface of the substrate; forming a color filter layerover the planarization layer; patterning the color filter layer todefine a space between adjacent color filters; forming a layer of anopaque material over the patterned color filter layer; and etching backthe opaque material until the color filter layer is exposed.
 14. Themethod of claim 13, wherein the forming the layer of the opaque materialincludes forming a layer of a black photoresist.
 15. The method of claim10, further comprising: forming a plurality of metal layers over thefront surface of the substrate; and forming an intermetal dielectricbetween each of the plurality of metal layers.
 16. A semiconductordevice, comprising: a substrate having a front surface and a backsurface; a plurality of pixels formed on the front surface of thesubstrate, each pixel being adapted to sense light radiation directedtowards the back surface of the substrate; an array of color filtersformed over the back surface of the substrate, each color filter beingaligned with one of the plurality of pixels for allowing a wavelength oflight radiation to pass through to the one of the plurality of pixels; aplurality of micro-lens formed over the array of color filters, eachmicro-lens being adapted to direct light radiation to each color filterin the array; and a blocking structure disposed between the back surfaceof the substrate and the plurality of micro-lens, the blocking structurebeing adapted to block light radiation traveling towards a regionbetween adjacent micro-lens from reaching the pixels.
 17. The device ofclaim 16, wherein the blocking structure includes a black photoresistdisposed in a region between adjacent color filters.
 18. The device ofclaim 16, wherein the blocking structure includes a planarization layerformed between the back surface of the substrate and a bottom surface ofthe array of color filters, the planarization layer having a blackphotoresist disposed underneath an area between adjacent color filters.19. The device of claim 16, wherein the wavelength of light is one of ared light, a green light, and a blue light.
 20. The device of claim 19,wherein each pixel includes a photodiode and at least one transistor.